Discussing water in a cannabis growing forum is like talking about oil in a motorcycle forum. Everyone has an opinion on the subject and you’ll earn piles of information, good and bad. At the end of the day, hydroponically grown cannabis will be much more sensitive to pHa measure of the acidity or alkalinity of a solution More as compared to soil-grown cannabis. You also want to be aware of the total dissolved solids (TDStotal dissolved solids More) of water. A TDStotal dissolved solids More that’s too high makes hydro nutrient schemes very difficult. Let’s take a look at the options.
Softened water
If you take nothing else away from this article, take this: NEVER use “soft” water created in home water softener systems. It will sicken or kill plants of all kinds, plain an simple.
Distilled water
Store bought distilled water, by the gallon, is probably the most expensive of options. It’s usually great water to start with regardless of how you are growing, but you’ll pay for it – literally. That said, you might be able to save some money if you buy it in bulk (5 gallons) with reusable containers.
Reverse osmosis (RO) water
A main stay for many growers, a small RO unit can provide enough pure water for a small grow. They are relatively easy to install and will quickly pay for themselves if compared strictly to purchasing distilled water.
Rain water
Apart from the collection setup, rain water is nearly free and falls from the sky in a condition great for use in a home grow. Painted steel and painted aluminum roofing makes for reasonably good water, though you should be aware that any dust, pollen, and other sediments that collect on your roof will also show up in your reservoir. Additionally, using a rusty galvanized roof or composite shingle roof are terrible ideas. Iron-oxide and/or the petroleum bases of the composite shingles contaminate water and shouldn’t be used.
Activated charcoal-filtered water
Brita pitches and the like use a small activated charcoal filter than can do an admirable job of removing chlorine, flouride, minerals, and other dissolved solids from water prior to use. It also tends to bring most water toward neutral (pHa measure of the acidity or alkalinity of a solution More 7.0). If you choose to use this option you should change your charcoal filter as recommended because an old filter will fail miserably at purification. This can be an affordable solution and a clever DIY home grower can easily make their own activated charcoal filter.
Tap water
Along with well water, this is probably the most commonly available and least expensive of all water sources. A call to your local water provider will easily result in water quality tests that they must provide upon request. Most public utility tap water in Missouri will be alkaline (pHa measure of the acidity or alkalinity of a solution More ~8.0) and have 200-400 PPMparts per million More TDStotal dissolved solids More. Although this is a difficult starting point for hydroponics, organic living soils (OLSOrganic Living Soil More) are much more tolerant and you can grow some fine medicine without any treatment of the water what-so-ever. Bear in mind that use of tap water will likely shorten the lifespan of OLSOrganic Living Soil More and, over the course of a year, may spoil your soil due to accumulation of solids like calcium carbonate.
We hope you have already determined that the choice of a source for water is driven by your choice in cultivation methods. This article only brushes the surface in regards to water and water quality, but the reader should know that water quality can be absolutely critical – particularly for hydroponic growing.
Have you had success using one or more of these methods? We’d love to hear about it. We don’t mind hearing about the failures either.
Happy Harvests!
— The Lit Farmer —